1. Field of the Invention
This invention pertains generally to the field of aerodynamic surfaces on aircraft structure. With greater particularity, this invention pertains to a vortex control device for use on the exterior of an aircraft. With greatest particularity, this invention pertains to a vortex control device which mounts to movable cowling structure and extends cantilevered over adjacent stationary cowling structure so that a single continuous aerodynamic surface is presented to the air flow in an optimum position.
2. Description of the Related Art
Devices to lower the stall speed of aircraft to thereby improve aircraft aerodynamic performance are known in the art. For example, vortex control devices which have been mounted to aircraft engine nacelles to aerodynamically interact with airflow around the wing have been used to lower aircraft stall speed, thereby enabling lower landing speeds and safer short field operations. U.S. Pat. No. 4,540,143 to Wang et al., commonly assigned with the present invention and incorporated by reference herein, describes one such wake or vortex control device. This device is mounted to the exterior surface of an aircraft engine nacelle below and forward of the leading edge of the wing. The wake control device generates a vortex which sweeps back and over the top of the wing to control air flow, resulting in a lower aircraft stall speed which enables lower landing speeds and thereby increases the safety and short field performance of the aircraft.
When such devices are mounted in their aerodynamically optimum position, they must often bridge movable cowling structure such as cowl doors and nonmovable or stationary cowling structure on the nacelle. This has required that the wake control device be manufactured in two or more segments so that each can be separately mounted to the nacelle. Dividing the wake control device into two or more segments to achieve optimum positioning on the nacelle surface requires precision alignment of the two segments in order to maximize the beneficial effect, and introduces aerodynamic inefficiency at the gap between segments.
In the past, if the placement of the vortex control device was across a movable joint such as between the inlet fan cowl and the fan cowl thrust reverser for example, the vortex control device would be split at the joint and attached to each cowling piece separately, or the vortex control device would be moved to a non-optimum position to avoid the joint or the vortex control device would be reduced in size to avoid the joint. Splitting the vortex control device causes alignment problems, reduces efficiency and increases drag. Moving or reducing the size of the vortex control device causes a reduction in effectiveness of the vortex control device since now it is no longer optimized. The installed position and size of the vortex control device is critical to ensure proper air flow over the wing and proper positioning of the vortex which this device generates.